Organic base hydrogenofluorosulphonates, their use in releasing organic bases from their fluorohydrate, method of preparation thereof, compound containing them

ABSTRACT

The invention features the use of fluorosulphonates to release the organic bases from their fluorohydrate. This use is characterised in that a hydrogenofluorosulphonate of an organic base is formed and in that the hydrofluoric acid which is associated with the said base or with one of its precursors is separated therefrom. The invention is useful in organic synthesis applications.

The present invention relates to the use of fluorosulphonates to releaseorganic bases from their hydrofluoride, to hydrogen fluorosulphonates ofan organic base, to processes for the preparation of fluorosulphonate(s)and to compositions of organic base fluorosulphonate(s) and ofhydrofluoric acid. The invention relates more particularly to atechnique for separating hydrofluoric acid from organic bases capable offorming combinations, usually constituting defined compounds, withseveral, at least three, molecules of unitary hydrofluoric acid (i.e.HF).

The process according to the present invention is particularly suitablefor bases which constitute, with hydrofluoric acid, combinationscontaining more than two, advantageously three, hydrofluoric acid units.

It is well known to those skilled in the art that organic bases form,with hydrofluoric acid, complexes containing at least three hydrofluoricacid units. Generally, the weaker and softer the bases, the greater thenumber of hydrofluoric acid units per basic function.

Now, on account of their specific properties, fluoro compounds are inever-increasing demand and used in applications such as agriculture andhealth.

Fluoro derivatives are often difficult to synthesize and often involveexchanges of various substituents with fluorine. Now, the reagent mostcommonly used and the cheapest for carrying out the exchange isundeniably hydrofluoric acid.

In addition, this acid is increasingly being used as a reaction medium.Certain precursors of organic bases present problems of stability, thus,carbamoyl fluorides show thermal instability which leads to theformation of isocyanate or to the formation of fluorophosgene (Hoechst,EP 639,556) which is very difficult to handle on account of itstoxicity. Moreover, fluorophosgene leads to the loss of two fluorineatoms.

Accordingly, one of the aims of the present invention is to provide aform of organic bases whose use allows appreciable recovery of thehydrofluoric acid.

Another aim of the present invention is to provide a form of the abovetype whose use allows the hydrolysis of carbamoyl fluorides withoutreleasing phosgenes and in particular fluorophosgenes.

Another aim of the present invention is to provide a process forpreparing a form of the above type.

Another aim of the present invention is to provide a process forpreparing a form of the above type which allows the release of the basefrom carbamoyl.

Another aim of the present invention is to provide a compositioncontaining the said organic base and at least two equivalents ofhydrofluoric acid per basic function, from which composition recovery ofthe hydrofluoric acid is easy.

These aims and others which will emerge later are achieved by means ofusing the hydrogen fluorosulphonate form of an organic base in order toseparate it from the hydrofluoric acid which is combined with the saidbase or which is combined with one of its precursors.

Thus, in the course of the study which led to the present invention, ithas been shown that fluorosulphonic acid (HFSO₃) is capable ofdisplacing complexes between organic bases and hydrofluoric acid, thusallowing the hydrofluoric acid to be recovered.

The present invention is especially of interest for certain bases, inparticular phosphorus bases and especially nitrogen bases.

Thus, when the said base is a nitrogen base, it is advantageously chosenfrom amines (including cyclic amines) and imines (including aromaticheterocycles).

When the said base is a phosphorus base, it is advantageously chosenfrom phosphines (including cyclic phosphines), and aromatic heterocyclescontaining a phosphorus as hetero atom.

The greater the capacity of the said organic base to combine withhydrofluoric acid and the greater the number of hydrofluoric acid unitswith which it can combine, the greater the advantage of the presentinvention.

Thus, it is advantageous for the said organic base to be chosen fromthose whose pKa in combined form is not more than 8, advantageously notmore than 7.

The said base is chosen from those capable of forming complexes withhydrofluoric acid in which the ratio between the hydrofluoric acid andthe basic function (or at least one of the basic functions when themolecule treated contains several basic functions) is at least equal to5.

As has been outlined above, the said base is combined with hydrofluoricacid in the form of one of its precursors.

According to one particularly advantageous embodiment of the presentinvention, the said precursor is a precursor which releases the saidbase by consuming a molecule of water. This characteristic has anadvantage during the in-situ preparation of the fluorosulphonate anion,as will be seen later.

According to an advantageous variant of the present invention, in thesaid precursor, the function which will be converted into a basicfunction is a function which releases a gas such as, for example, carbondioxide.

When the said base is an amine (including an aniline), a good example ofa function which releases a gas (carbon dioxide) can be found incarbamic acid derivatives, such as urea, carbamoyl [often in the form ofhalide, usually fluoride] or carbamate functions. These functions arederived from isocyanate functions.

Given its cost, its relative instability and its corrosiveness, it isadvantageous for the said hydrogen fluorosulphonate to be formed insitu.

Accordingly, one of the aims of the present invention is to provide aprocess which makes it possible to release a base from one of itscomplexes with hydrofluoric acid.

This aim and others which will become apparent later are achieved bymeans of a process which includes a step a) in which the hydrogenfluorosulphonate of the said organic base is formed.

Advantageously, this process includes, after step a), a step b) in whichthe hydrofluoric acid is recovered from the composition thus modified.

It is possible to form the hydrogen fluorosulphonate by a simple actionof fluorosulphonic acid on the complex between the hydrofluoric acid andthe said organic base. This is undoubtedly a satisfactory route when aninexpensive source of such an acid is available on site.

However, it is advantageous, and this is another aim of the presentinvention, to be able to prepare fluorosulphonate in situ, in particularfrom a composition containing hydrofluoric acid, optionally combinedwith an organic base.

Thus, in the course of the study which led to the present invention, ithas been shown that fluorosulphonic acid can readily be manufactured insitu by the action of sulphuric acid or sulphur trioxide (sulphuricanhydride or SO₃) on more or less anhydrous organic compositionscontaining hydrofluoric acid.

When the said composition is wet and/or contains no dehydrating agent,it is then advisable to use sulphur trioxide, SO₃, in its native form orin the form of oleum.

If the said composition contains a dehydrating agent, it may then beadvantageous to use sulphuric acid, optionally containing a small amountof water (sulphuric acid at a concentration at least equal to 80%,advantageously to 90%, often to 95%). Thus, in this embodiment of thepresent invention, the fluorosulphonic acid is manufactured in situ bythe action of sulphuric acid on the hydrofluoric acid from thecomposition in the presence of a dehydrating agent.

Advantageously, the said dehydrating agent is a precursor of the saidbase.

The said organic base is an amine and the said precursor of the saidbase is an isocyanate function or a function which is derived therefrom(for example carbamoyl urea [halide, usually fluoride] or carbamate).

The reaction for the synthesis of the fluorosulphonic anion is carriedout at a temperature of between 0° C. and 100° C., distillationtemperature of HF, advantageously between 0° C. and 50° C., preferablybetween 0° C. and 20° C.

Although it is possible to envisage carrying out the said recovery ofthe hydrofluoric acid in a different manner, and in particular by liquidextraction, it is generally preferred for step b) of hydrofluoric acidrecovery to be a distillation.

The present process is particularly advantageous for recycling the baseacid reagents which are increasingly being developed, in particularreagents consisting of aromatic heterocycle(s), and of hydrofluoricacid, for which family of reagents the compound [pyridine, 10HF] can beconsidered a prime example.

It can also be especially advantageous for the release of thoseso-called organic bases (particularly advantageous also for thecorresponding fluorosulphonates) which contain at least one fluorophoriccarbon or sulphur.

Advantageously, the said organic base contains at least onesp³-hybridized carbon or an SF₅ as fluorophoric carbon or sulphur,respectively.

Advantageously, the said organic base contains at least one trivalentphosphorus or nitrogen atom as basic function, this atom, it goeswithout saying, containing a proton-accepting lone pair.

In order for the process to be particularly advantageous, the said baseneeds to be stable in very acidic and/or very dehydrating medium (mediumsimilar to olea [also referred to by some as oleums]).

Another aim of the present invention is to provide compounds which allowthe organic bases to be released from their complexes with several unitsof hydrofluoric acid, and in particular using compositions containing ahigh proportion of hydrofluoric acid—in general at least two units ofhydrofluoric acid, advantageously at least 3 and preferably at least 4units of hydrofluoric acid.

These aims and others which will become apparent later are achieved bymeans of the hydrogen fluorosulphonate of an organic base; it isdesirable for the said organic base, including the combined acid, tohave at least one basic function whose pKa is (measured or brought intoaqueous phase) not more than 10, advantageously not more than 8,preferably not more than 6. It is desirable for this pKa to be positiveand advantageously at least equal to 1, preferably at least equal to 2.Thus, organic bases whose pKa is between 1 and 8, preferably 2 and 6(limits included) are preferred.

Organic bases whose hydrogen fluorosulphonate is targeted by the presentinvention, and which contain at least one fluorine atom, advantageouslyat least two fluorine atoms, are of special industrial interest. This orat least one of these fluorines is advantageously borne by an atom whichhas no aromatic nature (i.e. by an atom which is not a member of anaromatic ring) this fluorophoric atom (i.e. fluorine-bearing atom), whenit is carbon, is preferably sp³-hybridized; besides the fluorine atomwhich gives this fluorophoric atom its title, the latter atomadvantageously bears one or two (identical or different) halogen atoms[preferably chosen from light halogens, i.e chlorine or fluorine].

In other words, the said organic base whose hydrogen fluorosulphonate istargeted by the present invention, advantageously contains at least one,preferably at least two, fluorine atoms. It is also preferable for it tocontain at least one fluorine on an sp³-hybridized carbon, whichadvantageously bears one or two (identical or different) halogen atoms[preferably chosen from light halogens, i.e. chlorine or fluorine]. Itis thus desirable for the organic base, whose hydrogen fluorosulphonateis targeted by the present invention, to contain as fluorophoric atom atleast one carbon or at least one chalcogen from an atomic row at leastequal to that of sulphur; organic bases which contain as fluorophoricatom(s) at least one sp³-hybridized carbon or a hexavalent chalcogen(which, of course, cannot be oxygen), preferably sulphur (for exampleSF₅), are more particularly targeted.

Advantageously, the said fluorophoric atom (for example sp³-hybridizedcarbon or hexavalent sulphur) bears at least two fluorine atoms.

The said organic base advantageously contains, as atom bearing the (orone of the) basic function(s) (i.e. proton accepter), a nitrogen or atrivalent phosphorus.

Among the advantageous bases, mention may be made of aromaticheterocycles such as pyridines, including quinolines, which areoptionally substituted, including substitution with halogens (chlorine,fluorine, bromine, etc.) and optionally bearing, indirectly or, moreadvantageously, directly, at least one fluorophoric atom as definedabove.

These bases advantageously correspond to the following formula:

Ar—L—′A—F_(q)(R)_((v−q))

with Ar representing a base of aromatic nature in which the hetero atombearing the (or one of the) basic function(s) (i.e. proton accepter) iseither endocyclic (as in the case of pyridine or quinoline) or exocyclic(as in anilines);

with L representing a bond between Ar and ′A; with ′A representing thefluorophoric atom as defined above;

q represents the number of fluorine atoms borne by the said fluorophoricatom and is at least equal to one and not more than v;

v represents the residual valency (i.e. valency available after the bondbetween L and ′A has been taken into account) of the fluorophoric atom;the groups R, which may be identical or different, (of course when v>q)represent halogens, hydrogen atoms, a carbon-based chain or can containone or more other fluorophoric atoms.

R can attach to a position of Ar to form a ring (this ringadvantageously being 4- to 8-membered, preferably 5- to 7-membered); inthis case, R can advantageously take the values of L and in particularcan simply be a chalcogen (in particular oxygen or sulphur) or a singlebond.

L is advantageously chosen from a single bond, a chalcogen atom and adivalent carbon-based radical which can contain one or more fluorophoricatoms. In the case of a divalent carbon-based radical, the bond betweenL and Ar can be an sp² carbon-chalcogen bond; moreover, it may beadvantageous for the bond between L and the fluorophoric atom to be achalcogen-fluorophoric atom bond.

Ar can optionally be substituted on its available ring members,including substitution with halogens (chlorine, fluorine, bromine, etc.)and/or with other substituents corresponding to the formula:

—L—′A—F_(q)(R)_((v−q)) detailed above:

thus, Ar represents a base of aromatic nature in which the hetero atombearing the (or one of the) basic functions) (i.e. a proton accepter) iseither endocyclic (as in the case of pyridine or quinoline) or exocyclic(as in anilines).

Ar advantageously contains not more than about 40 carbon atoms,preferably not more than about 30, each R advantageously containing notmore than about 10 carbon atoms, preferably not more than 8. Ladvantageously contains not more than about 10 carbon atoms, preferablynot more than 8.

The total number of carbon atoms in the base is advantageously not morethan about 50 carbon atoms, preferably not more than 30 carbon atoms.

Mention should be made of a base sub-family in which ′A—F_(q)(R)_((v−q))represents a perfluoro radical (i.e. R_(f)=C_(n)F_(2n+1)).

Mention should be made of a base sub-family in which L represents asingle bond or a chalcogen atom.

The intersection between these two sub-families is particularlyadvantageous.

The present invention thus relates to a composition containing bothhydrofluoric acid and a hydrogen sulphonate, in which composition themolar ratio between the hydrofluoric acid and the basic functions of thesaid organic base (HF/basic functions of the said organic base) is atleast equal to 2, advantageously equal to 3, preferably equal to 4.

The water content in the said composition is advantageously such thatthe number of molecules of water in the composition is not more thanhalf (advantageously a quarter, preferably a tenth) of the number(expressed as equivalents) of basic functions present in thecomposition.

In addition, the composition can also contain sulphuric acid.

Needless to say, it can also contain any product used in the previoussteps of the synthesis of the said organic base.

The non-limiting examples which follow illustrate the invention.

General conditions and general procedure

The crude reaction products were analysed by gas chromatography.

Principle

As indicated in the above description, it is economically important andwas technically conceivable to recover the excess HF used to fluorinatethe last but one precursor of the pTFMA by distillation after the stepof lysis of the carbamoyl fluoride into pTFMA hydrofluoride:

After unsuccessfully attempting to recover the “free” HF by distillingthe pTFMA hydrofluoride/HF mixture, the lysis technique was testedaccording to a particularly advantageous embodiment of the presentinvention, by addition of 98% sulphuric acid to the PTFMAhydrofluoride/HF mixture.

EXAMPLE 1 (COMPARATIVE) Distillation of HF using a DTF hydrofluoride/HFmixture

The assay for this sample (neutralization, pTFMA assay by HPLC, assay ofthe fluorides by ion chromatography) gives the following proportions:

pTFMA/HF=59/41

i.e. 5.6 equivalents of HF relative to the pTFMA.

Distillation procedure

Experimentally, the pTFMA hydrofluoride/HF mixture was heated in a 500ml Teflon PFA reactor under a stream of nitrogen. The HF distilled offwas trapped out in bubblers with potassium hydroxide, the fluoridesbeing assayed by ion chromatography.

The distillation vessel was heated until an HF distillation plateau wasreached without degradation of the trifluoromethylaniline.

The results are collated below:

Test Initial pTFMA Dura- pTFMA* No. hydrofluoride HF T° tion HFdistilled off found a pTFMA: 0.198 mol 60° C. 1h 30 0.078 mol, i.e. 96%HF_(free): 0.911 mol 8.5% of the initial “free” HF b crude product 90°C. 1h 00 0.162 mol, i.e. 100%  from a) 19.5% of the remaining “free” HFTotal 26% of the 98% initial “free” HF *assay by HPLC afterneutralization.

It appears that heating the PTFMA hydrofluoride/HF mixture allows only26% of the “free” HF (HF not in hydrofluoride form) initially present tobe distilled off.

The remaining HF associated with the PTFMA would appear to correspond toa complex of approximate formula:

pTFMA·4HF

These HF-base complexes are known to be difficult to decompose by simpleheating.

In conclusion, heating of the pTFMA hydrofluoride/HF crude reactionproduct does not allow all of the HF initially present to be recycled.

EXAMPLE 2 Tests of recovery of HF from carbamoyl fluoride. 6HF

It was possible to observe that simple addition of 98% sulphuric acid tocarbamoyl fluoride led to a considerable and immediate evolution of gas.

Infrared analysis of the gas formed demonstrates that it is essentiallycarbon dioxide. It appeared that the result of the above case was found.However, analyses on the crude reaction product and further studies madeit possible to explain the formation of CO₂ by reaction betweencarbamoyl fluoride and H₂SO₄: the sulphuric acid (even at 100%) reactswith it to form pTFMA fluorosulphonate and CO₂.

TABLE II

Treatment of the pTFMA · nHF mixture with H₂SO₄

H₂SO₄: quality and No. of equiv. relative to the pTFMA T°, duration HFevolved pTFMA RY HF not distilled off pTFMA; HF: 100% H₂SO₄ 60° C., 2 h0.517 98% 1.1 0.098 mol; mol, equiv. HF: 0.629 mol i.e. of HF % i.e. 5.45.3 i.e = equiv. 2.1 equiv. 90° C., 1 h equiv. 0.1 equiv. of free HFpTFMA; HF: 98% H₂SO₄ 60-65° C., 0.65 97% HF: 1.16 0.097 mol; 2 h mol,equiv., HF: 0.709 mol i.e. i.e. i.e. 6.3 6.7 0.16 equiv. 2.08 equiv. 90°C., 1 h equiv. equiv. free HF pTFMA; HF: 98% H₂SO₄ 65° C., 2 h 0.53796.5% HF: 1.85 0.098 mol; mol, equiv., HF: 0.715 mol i.e. i.e. i.e. 6.35.48 0.85 equiv. 4 equiv. 90° C., 1 h equiv. equiv. of free HF pTFMA;HF: 98% H₂SO₄ 60-65° C., HF: 1.47 6.6 equiv. HF a) 1.13 1 h 30 equiv.,equiv. 3 i.e. 0.47 equiv. free HF b) additional 90° C., 1 h 98% HF: 1 1equiv. equiv., i.e. 0 equiv. free HF

To the Applicant's knowledge, this water-free “lysis” of a carbamoylhalide function with sulphuric acid has never been described in theliterature.

A 6-centre mechanism can be put forward to explain this reaction, theCF₃ group strongly activating the carbamoyl fluoride function:

The PTFMA fluorosulphonate, characterized by ¹⁹F NMR and IR was alsosynthesized by the action of fluorosulphonic acid HFSO₃ on pTFMA.

pTFMA fluorosulphonate is a solid which is rapidly hydrolysed byatmospheric moisture into PTFMA

Experimentally, the tests summarized in Table II were carried out in thefollowing way:

98 or 100% sulphuric acid was added to the above solutions at 20° C.,leading to an immediate evolution of CO₂.

After adding the H₂SO₄, the homogeneous reaction mixture was heated,under a stream of nitrogen, to remove the HF, which was trapped out inbubblers containing potassium hydroxide. The fluorides obtained wereassayed by ion chromatography.

After cooling to room temperature, the reaction media were analysed.After anhydrous neutralization with pentylamine, the pTFMA was assayedby HPLC.

From the results obtained, the following conclusions can thus be drawn:

The action of about 2 equivalents of H₂SO₄ (98 or 100%) on a mixture, HF(5 to 6 equivalents of HF relative to the carbamoyl fluoride), followedby heating to 90° C. allows virtually all of the initial “free” HF to beremoved.

After removal of the HF, the medium obtained is homogeneous and liquid,and corresponds to a solution of pTFMA fluorosulphonate in H₂SO₄containing a small amount of HF (0.1 to 0.2 equivalent of initial “free”HF).

The use of 4 equivalents of 98% H₂SO₄ limits the number of equivalentsof HF distilled off. This can be explained by the water provided by the98% H₂SO₄ which can hydrolyse the carbamoyl fluoride into PTFMAhydrofluoride. In this case, HF-base complexes can be formed between thebase and the HF and limit the distillation of the HF, as has alreadybeen observed.

This type of HF-base complex should not be formed between pTFMAfluorosulphonate and HF.

After neutralization of the crude reaction product which has beendegassed in respect of HF, the pTFMA was obtained in a yield of about97-98% (HPLC assay).

In conclusion, the addition of 2 equivalents of 98 or 100% H₂SO₄ to thecrude product from the fluorination of pTCMI 2 makes it possible, byheating, to recycle virtually all of the free HF initially present andto obtain a homogeneous liquid solution of PTFMA fluorosulphonate 7 inabout 1 equivalent of H₂SO₄.

Using the solution of PTFMA fluorosulphonate in sulphuric acid afterdistillation of the HF, the pTFMA can be obtained by neutralization withaqueous sodium hydroxide and extraction with methylene chloride. Theyield for this neutralization and extraction step is greater than 98%.

What is claimed is:
 1. A method for the separation of the hydrogenfluorosulphonate form of an organic base from a mixture comprisingcombining hydrofluoric with the hydrogen fluorosulphonate form of anorganic base or one of its precursors and recovering said organic basefrom said mixture.
 2. The method according to claim 1, wherein said baseis a nitrogen base.
 3. The method according to claim 1, wherein saidbase comprises amines and imines.
 4. The method according to claim 1,wherein said base comprises phosphines and aromatic heterocyclescontaining a phosphorus as a hetero atom.
 5. The method according toclaim 1, wherein said base comprises compounds whose pKa in combinedform is not more than
 8. 6. The method according to claim 1, whereinsaid base comprises compounds capable of forming complexes withhydrofluoric acid in which the ratio between the hydrofluoric acid andthe basic functions is at least equal to
 5. 7. The method according toclaim 1, wherein said base is combined with hydrofluoric acid in theform of a precursor.
 8. The method according to claim 1, wherein saidprecursor is a precursor which releases said base by consuming amolecule of water.
 9. The method according to claim 1, wherein saidprecursor is a function which releases carbon dioxide.
 10. The methodaccording to claim 1, wherein said base is an amine and said precursoris a function which releases carbon dioxide.
 11. The method according toclaim 1, wherein said base is an amine and the precursor function is anisocyanate function or a function derived therefrom.
 12. The methodaccording to claim 1, wherein said hydrogen fluorosulphonate is formedin situ.
 13. Process for treating a composition containing an organicbase or its precursor and anhydrous hydrofluoric acid, comprising stepa) in which the hydrogen fluorosulphonate of said organic base isformed.
 14. Process according to claim 13, further comprising, afterstep a), a step b) in which the hydrofluoric acid is recovered from thecomposition thus modified.
 15. Process according to claim 13, whereinthe fluorosulphonic acid is manufactured in situ by the action ofsulphuric acid or sulphur trioxide (SO₃) on said composition. 16.Process according to claim 14, wherein the fluorosulphonic acid ismanufactured in situ by the action of sulphuric acid on the hydrofluoricacid from the composition in the presence of a dehydrating agent. 17.Process according to claim 16, wherein said dehydrating agent is theprecursor of said base.
 18. Process according to claim 17, wherein saidorganic base is an amine and said precursor of said base is anisocyanate function or a function which is derived therefrom. 19.Process according to claim 18, wherein the reaction is carried out at atemperature of between 0° C. and 100° C.
 20. Process according to claim19, wherein said recovery of the hydrofluoric acid in step b) is adistillation.
 21. Process according to claim 1, wherein said recovery ofthe hydrofluoric acid in step b) is an extraction.